A car navigation device has a function for reading text-information (i.e., mail information, SNS (social networking service) information and the like) aloud to a driver using voice synthesis technique, in addition to a function for providing voice guidance of a route to a destination (see Patent Literature 1). The device sets a reading-aloud mode automatically in accordance with an input source of the text information or a content of the text information. Further, the device specifies a combination of voice synthesis control parameters corresponding to the reading-aloud mode, so that the device synthesizes a voice. According to the device, when a volume of the mail information is large, a reading-aloud speed becomes high, so that reading-aloud time is reduced. Further, when the device reads route guidance information and traffic information, the reading-aloud speed for a distance and a geographical name becomes low, so that a passenger can catch the sound.
The above device sets the reading-aloud mode according to the content of the text information or the input source (i.e., a type of an application program) of the text information. Accordingly, the device does not have a construction for reading aloud at a timing suitable for the driver with consideration to safety of the driver. Specifically, when the vehicle is in a stop condition so that the driver reads the text information by himself or herself, it is not always necessary to read aloud automatically. Instead, since the driver reads the text information by himself or herself, the automatic reading-aloud is very bothersome. When the vehicle is in a running condition so that the driver cannot read the text information, it is necessary to read aloud automatically because of the safety.